Method and system for configuring device-to-device communication

ABSTRACT

A method and system for use in an advanced wireless communication network is provided. The method comprises: providing, to a group of UEs, a resource multiplexing configuration defining resource multiplexing for cellular and non-cellular communication; and allocating resources to the group of UEs for cellular communication, according to the resource multiplexing configuration. Advantageously, the method enables collisions and interference between D2D and cellular transmissions to be reduced or avoided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/902,508 filed on Jun. 16, 2020, which is issuedas U.S. Pat. No. 11,398,881, which is a continuation application of U.S.patent application Ser. No. 16/199,696 filed on Nov. 26, 2018, which isissued as U.S. Pat. No. 10,735,144, which is a continuation applicationof U.S. patent Ser. No. 15/303,635 filed on Oct. 12, 2016, which isissued as U.S. Pat. No. 10,200,159, which is a National Stage Entry ofinternational application PCT/JP2015/001402 filed on Mar. 13, 2015,which claims the benefit of priority from Australian Patent ApplicationNo. 2014901540 filed on Apr. 29, 2014, the disclosures of all of whichare incorporated in their entirety by reference herein.

BACKGROUND ART Abbreviations

The following abbreviations are used herein:

ACK Acknowledgement D2D Device to Device Communication D2D-UE CellularUser equipment with direct communication capability DL Downlink ePDCCHenhanced Physical Downlink Control Channel FDD Frequency DivisionDuplexing FDM Frequency Division Multiplexing HARQ-ACK Hybrid AutomaticRepeat Request Acknowledgement LTE Long Term Evolution NAK NegativeAcknowledgement PDCCH Physical Downlink Control Channel PDSCH PhysicalDownlink Shared Channel PHICH Physical Hybrid ARQ Indicator Channel QoSQuality of Service RRC Radio Resource Control SF Subframe TDD TimeDivision Duplexing TDM Time Division Multiplexing UE User Equipment ULUplink

Recent advancements in the field of wireless communication includesutilising spectrum generally allocated for cellular communication forinstead performing direct communication between one mobile device andanother mobile device, or among a group of mobile devices within thelocal vicinity. This is widely known as device-to-device (D2D)communication or peer-to-peer (P2P) communication. Direct communicationbetween mobile devices with or without the coordination of an overlaycellular communication network may have many advantages including, butnot limited, to improving overall spectral efficiency, improving localcoverage, facilitating traffic offloading from a cellular network andenabling various types of new services and applications.

SUMMARY OF INVENTION Technical Problem

D2D communication can generally be performed in two ways, namely networkcontrolled D2D and autonomous D2D. Network controlled D2D can beperformed in both FDD and TDD cellular networks with either shared UL orDL resources or with dedicated D2D resources. Autonomous D2Dcommunication may operate in a dedicated spectrum for D2D, or inunlicensed spectrum. In comparison to autonomous D2D, network controlledD2D may more efficiently utilise network resources and thus providebetter quality of service (QoS) levels.

Currently, there are no suitable methods to configure D2D and cellularresource multiplexing in TDD and FDD cellular systems. Accordingly,there is a need for an improved method and system for configuring D2Dcommunication.

It will be clearly understood that, if a prior art publication isreferred to herein, this reference does not constitute an admission thatthe publication forms part of the common general knowledge in the art inAustralia or in any other country.

Solution to Problem

The present invention is directed to control signalling in advancedwireless communication networks, which may at least partially overcomeat least one of the abovementioned disadvantages or provide the consumerwith a useful or commercial choice.

With the foregoing in view, the present invention in one form, residesbroadly in a method for use in an advanced wireless communicationnetwork, the method comprising:

providing, to a group of UEs, a resource multiplexing configuration thatdefines resource multiplexing for cellular and non-cellularcommunications; and

allocating resources to the group of UEs for cellular communication,according to the resource multiplexing configuration.

Advantageously, the resource multiplexing configuration enablescollisions and interference between non-cellular (e.g. D2D) and cellulartransmissions to be reduced or avoided.

According to certain embodiments, the non-cellular communicationcomprises device-to-device (D2D) communication.

According to other embodiments, the method further comprises receiving,from a UE of the group of UEs, a request to allocate resources fornon-cellular communication, wherein the resource multiplexingconfiguration is provided to the group of UEs in response to therequest.

According to certain embodiments, the resource multiplexingconfiguration includes a resource multiplexing mask defining a resourceallocation pattern for cellular and non-cellular communication. Theresource multiplexing mask can be defined by a bitmap. The bitmap candefine a resource allocation for at least one radio frame of theresource allocation pattern. Each bit of the bitmap can define whether asubframe is allocated to cellular or non-cellular communication.

The resource multiplexing configuration can define fixed resources forcellular communication, and flexible resources that can be allocated forcellular or non-cellular communication. In such case, the resourcemultiplexing mask can be defined by a bitmap, wherein each bit of thebitmap defines a resource allocation for the flexible resources.

As certain resources are fixed for cellular communication, i.e. cannotbe used for non-cellular communication, it is not required to explicitlysignal any resource allocation to the group of UEs. As a result,signalling overhead can be reduced by not explicitly signalling resourceallocations for resources that are fixed for cellular communication.

According to certain embodiments, the resource multiplexing mask definesa resource allocation for 10 consecutive subframes, wherein a firstthree subframes of the resource multiplexing mask are permanently fixedfor cellular communication. As a result only 7 bits are required tosignal the resource multiplexing mask.

According to other embodiments, the resource multiplexing mask defines aresource allocation for 10 consecutive subframes, and wherein subframes0, 1, 2, 5 and 6 of the resource multiplexing mask are fixed forcellular communication.

In LTE TDD systems, subframes 0, 1, 5 and 6 carry importantchannels/signals such as PSS, SSS and paging channels. If thesesubframes are allocated for D2D communication, the D2D-UEs involved inthat communication may fail to receive and decode system information andmessages on these subframes.

According to yet other embodiments, the resource multiplexing maskdefines a resource allocation for 10 consecutive subframes, and whereinsubframes 0 and 5 of the resource multiplexing mask are fixed forcellular communication.

In LTE FDD systems, DL subframes 0 and 5 may carry important signalssuch as PSS and SSS. If these subframes in DL spectrum are allocated forD2D communication, the D2D-UEs involved in that communication may failto maintain synchronisation with the cellular system.

According to other embodiments again, the resource multiplexing maskdefines a resource allocation for 10 consecutive subframes, and whereinsubframes 0, 4, 5 and 9 of the resource multiplexing mask are fixed forcellular communication.

In an LTE FDD system, in addition to DL subframes 0 and 5 being used forPSS, SSS and paging, DL subframes 4 and 9 can also be used for pagingchannel transmission. If these subframes in DL spectrum are allocatedfor D2D communication, the D2D-UEs involved in that communication mayfail to receive and decode paging information intended for them. Ifthese subframes in UL spectrum are allocated for D2D communication,there may be severe in-device interference at receiving D2D UEs whosimultaneously receive cellular DL and D2D signals in UL spectrum, inwhich case the important system information would be interfered by D2Dreception.

According to certain embodiments, the method further comprisesproviding, to a second group of UEs, a second resource multiplexingconfiguration defining resource multiplexing for cellular andnon-cellular communication; wherein the resource multiplexingconfiguration and the second resource multiplexing configuration areconfigured to minimise interference between the group of UEs and thesecond group of UEs.

The resource multiplexing configuration can be defined in acommunication interval in an integer number of radio frames, thecommunication interval defining resource multiplexing for a plurality ofgroups of UEs, the resource multiplexing configuration defined by aconfiguration offset, and the configuration offset defining an offset ofa configuration interval with respect to the communication interval.

Advantageously, the configuration offset T₀ allows the base station toseparate D2D communication resources of different groups of UEs in time,thus providing time-domain interference management.

The second resource multiplexing configuration can be defined in thecommunication interval, the second resource multiplexing configurationdefined by a second configuration offset, and the second configurationoffset defining an offset of a second configuration interval withrespect to the communication interval.

The communication interval can comprise one of: one; four; eight;sixteen; thirty two; or sixty four radio frames, and be repeatedperiodically once configured. Similarly, the configuration interval cancomprise one of: one, four or eight radio frames.

The resource multiplexing configuration can be at least partly providedby an RRC message. Similarly, resources can be at least partly allocatedfor cellular or non-cellular communication dynamically by TDD eIMTA.

The cellular communication can, for example, be FDD or TDD based.

The group of UEs can comprise a pair of UEs, or more than two UEs.

According to certain embodiments, the method further comprisesreceiving, from a UE of the group of UEs, a scheduling pattern for groupof UEs in relation to non-cellular communication. The scheduling patterncan be repeatedly applied by the UEs in the group of UEs to determinewhich UE should transmit in each configured non-cellular time interval.On a particular subframe or subframes in a scheduling pattern that isallocated to a particular UE for non-cellular communication, the UE maypiggyback ACK/NAK feedback associated with previously received data withits data transmission for feedback option or perform repetition of itsdata transmission. When the UE has piggybacked ACK/NAK feedback with itsdata transmission, re-transmission of a message can be performed if, atthe next transmission opportunity, either all received feedback areNAKs, or if no feedback is received. Alternatively, a number ofrepetitions can be predefined for being combined decoding or selectivedecoding at a receiver or receivers.

In another form, the present invention resides broadly in a system foradvanced wireless communication, the system, including:

a group of UEs; and

a base station, the base station including:

-   -   a transmitter;    -   a processor coupled to the transmitter; and    -   a memory coupled to the processor, the memory including        instruction code executable by the processor for:        -   providing, to a group of UEs, a resource multiplexing            configuration defining resource multiplexing for cellular            and non-cellular communication; and        -   allocating resources to the group of UEs for cellular            communication, according to the resource multiplexing            configuration.

Advantages of certain embodiments of the present invention include anability to provide a method to configure cellular and D2D resourcemultiplexing that allows time-domain interference management between D2Dgroups/pairs.

Certain embodiments of the present invention provide a method for a basestation to provide one of several possible resource multiplexingconfigurations to D2D-UEs or D2D groups using a resource multiplexingmask and/or and optimised bitmap for TDD and FDD.

Other embodiments provide four different resource multiplexing masksthat can be used to cover almost every D2D and cellular multiplexingconfiguration in TDD and FDD. These resource multiplexing masks canenable the reception of important system information in TDD and FDDsystems, and avoid possible cellular and D2D transmission collisions inTDD by allowing for the use of reference configurations for HARQ-ACK, ULgrant and PHICH timing.

Embodiments of the present invention provide a simple, yet efficientmethod for performing D2D communication within D2D groups.

According to certain embodiments of the present invention, legacy LTEdevices are not impacted.

Any of the features described herein can be combined in any combinationwith any one or more of the other features described herein within thescope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Preferred features, embodiments and variations of the invention may bediscerned from the following Detailed Description which providessufficient information for those skilled in the art to perform theinvention. The Detailed Description is not to be regarded as limitingthe scope of the preceding Summary of the Invention in any way. TheDetailed Description will make reference to a number of drawings asfollows:

FIG. 1 is a schematic diagram illustrating a wireless communicationsystem, according to an embodiment of the present invention;

FIG. 2 illustrates a method of resource allocation for cellular and D2Dcommunication in a TDD/FDD system, according to an embodiment of thepresent invention;

FIG. 3 illustrates resource multiplexing masks and corresponding bitmapsfor multiplexing D2D and cellular resources in TDD systems, according toan embodiment of the present invention;

FIG. 4 illustrates resource multiplexing masks and corresponding bitmapsfor multiplexing D2D and cellular resources in FDD systems, according toan embodiment of the present invention;

FIG. 5 illustrates a plurality of resource multiplexing configurationsin TDD systems, according to an embodiment of the present invention;

FIG. 6 illustrates a method of resource allocation or multiplexing forD2D and cellular communication at a cellular base station, according toan embodiment of the present invention;

FIG. 7A illustrates a method for resource allocation or multiplexing forD2D and cellular at a D2D capable UE in an FDD system, according to anembodiment of the present invention;

FIG. 7B illustrates a method for resource allocation or multiplexing forD2D and cellular at a D2D capable UE in an FDD system, according to anembodiment of the present invention;

FIG. 8A illustrates a method for resource allocation or multiplexing forD2D and cellular at a UE in a TDD system, according to an embodiment ofthe present invention;

FIG. 8B illustrates a method for resource allocation or multiplexing forD2D and cellular at a UE in a TDD system, according to an embodiment ofthe present invention;

FIG. 9 illustrates a schematic of an exemplary cellular communicationscenario in an FDD system, according to an embodiment of the presentinvention;

FIG. 10 illustrates a schematic illustrating the procedures for cellularcommunication at base station, D2D-UEs and legacy UE in TDD system whencellular resources are shared by D2D-UEs for D2D communication,according to an embodiment of the present invention;

FIG. 11 illustrates a method of performing D2D communication within agroup of D2D UEs in resources allocated for D2D communication, accordingto an embodiment of the present invention; and

FIG. 12 illustrates a schematic of an exemplary D2D communicationscenario in a D2D group, and a schematic illustrating a correspondingtiming diagram, according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic diagram illustrating a wireless communicationsystem 100, according to an embodiment of the present invention. Thewireless communication system 100 enables transmission and reception ofcellular and D2D resource multiplexing configurations, as discussed infurther detail below.

The wireless communication system 100 is a typical single cell cellularnetwork comprising an access node 101 representing a cellular basestation providing a first coverage 101.a and services to plurality ofuser equipment (UE) 102-107. The access node 101 can be an FDD or a TDDaccess node.

Among the plurality of UEs 102-107, there may be more than one UE thatis capable of performing both cellular communication and direct/D2Dcommunication. The plurality of UEs 102-107 may further include a legacyUE (such as UE 105) that is capable of performing typical cellularcommunication 110 only.

According to one embodiment, D2D-UEs that are in close proximity to eachother, such as UEs 102, 103 and 104, may discover each other,synchronise to each other and form a D2D group for one-to-many groupcommunication or groupcasting, as illustrated by D2D group 102.a.

The D2D-UEs in such a D2D group may be configured by the base station101 to use cellular resources (UL resources, DL resources or both), orto directly communicate within the group. These D2D-UEs may thencommunicate with each other using a direct communication link 111, whilemaintaining a cellular communication link 108 with the base station 101on subframe basis. The cellular communication link 108 may be used bythe D2D-UEs for typical cellular communication (and maintaining RRCconnectivity), and for receiving and sending D2D communication relatedinformation such as D2D and cellular multiplexing configurationinformation, new group member detection information and D2D channelstate reports.

In another embodiment, when two D2D-UEs are in close proximity to eachother, as for example illustrated by UEs 106, 107, they may discovereach other, synchronise to each other and pair with each other to form adirect one-to-one communication pair, as illustrated by D2D-pair 106.a.These D2D-UEs may also be configured by the base station 101 to usecellular resources (UL resources, DL resources or both), or to directlycommunicate with each other using a direct communication link 112 whilealso maintaining a cellular communication link 109 with the base station101. The cellular communication link 109 may be used by the D2D-UEs fortypical cellular communication (and maintaining RRC connectivity), andfor receiving and sending D2D communication related information such asD2D and cellular multiplexing configuration information and D2D channelstate reports.

For the sake of clarity, the specification hereon refers to groups ofD2D-UEs as including a pair of D2D-UEs, or more than two D2D-UEs.

The system 100 provides a method to allocate resources for cellular andD2D communication, as described in further detail below. Allocatingresources for cellular and D2D communication can, for example, comprisemultiplexing cellular and D2D resources when D2D-UEs share cellularresources for D2D communication, as discussed below.

FIG. 2 illustrates a method 150 of resource allocation for cellular andD2D communication in a TDD/FDD system, according to an embodiment of thepresent invention.

A D2D communication interval 151 (denoted by T₁) is provided, whichincludes a D2D configuration interval 152 (denoted by T₂) and a D2Dconfiguration offset 153 (denoted by T₀). The D2D communication intervalT₁/151 may be configurable, e.g. to a user configured number of radioframes in an LTE communication system. Once being configured, the D2Dconfiguration interval T₁/151 is repeated until reconfigured orterminated.

The D2D configuration interval T₂/152 may be configured within a D2Dcommunication interval T₁/151 to last for 1 radio frame (as illustratedby 152.I), 4 radio frames (as illustrated by 152.II) or 8 radio frames(as illustrated by 152.III). Furthermore, a pattern can be provided toindicate on subframe level which subframes being allocated to cellularcommunication and which subframes being allocated to D2D communication.

According to certain embodiments, T₁ is configurable to span for oneradio frame (n1), four radio frames (n4), eight radio frames (n8),sixteen radio frames (n16), thirty-two radio frames (n32) or sixty-fourradio frames (n64).

The D2D configuration offset T₀/153 can be used to indicate at whichradio frame the D2D configuration interval T₂/152 starts, with referenceto the D2D communication interval T₁/151. The configurable D2Dconfiguration offset T₀/153 allows the system to have time-multiplexedintervals of D2D communication for different groups (or pairs) ofD2D-UEs, and thus enables time-domain interference management.

Furthermore, the D2D configuration interval T₂/152 may be less than orequal to the D2D communication interval T₁/151. The resourcemultiplexing pattern configured for the D2D configuration intervalT₂/152 is then started after the D2D configuration offset T₀/153, i.e.an amount of time (e.g. a number of radio frames in an LTE communicationsystem) from the beginning of the D2D communication interval T₁/151.

The D2D configuration offset T₀/153, the D2D communication intervalT₁/151, and the D2D configuration interval T₂/152 can be configuredusing RRC signalling. A sample of corresponding RRC signalling isillustrated in RRC sample 154.

In accordance with certain embodiments of the present invention, aresource multiplexing mask is used to indicate a resource allocationpattern for cellular and D2D communication within the D2D configurationinterval 152/T₂. The resource multiplexing mask may include fixedresource elements for cellular communication and flexible resourceelements that can be allocated for either cellular or D2D communication.The flexible resource elements can be configured by the base station 101via RRC messages in LTE communication. Furthermore, in the case that thesystem 100 supports TDD eIMTA, the flexible resource elements can bedynamically allocated for cellular or D2D communication on a radio framebasis.

The resource allocation pattern defined by the resource allocation maskis signalled to the D2D-UEs using a bitmap that is X bits long.According to certain embodiments, a bitmap of X=10 bits is used toindicate the resource allocation mask for a radio frame, where each bitwithin the 10-bit string indicates if a certain subframe within thatradio frame belongs to cellular communication or D2D communication.

According to alternative embodiments, described in further detail below,the bitmap is optimised for resource configuration in TDD and FDDsystems, and thus requires less than 10 bits.

FIG. 3 illustrates resource multiplexing masks and corresponding bitmapsfor multiplexing D2D and cellular resources in TDD systems, according toan embodiment of the present invention.

A first method 152.1 for optimising a bitmap for an LTE TDDcommunication system is illustrated, wherein a first resourcemultiplexing mask 155 of 10 time units/subframes is provided. The firstthree time units/subframes 156 of the first resource multiplexing mask155 are permanently fixed for cellular communication, and last sevensubframes 157 are flexibly allocated for either cellular communicationor D2D communication. This resource multiplexing pattern allows for allseven LTE TDD UL/DL configurations to have reference UL/DLconfigurations for cellular communication in D2D-UEs without HARQ-ACKand/or UL grant collisions.

As the first three time units/subframes 156 are fixed for cellularcommunication, the base station 101 does not need to signal thisinformation to the D2D-UEs, and as such, the bitmap can be reduced bythree bits. Thus, an optimised bitmap 160 for the resource multiplexingmask 155 is provided that is seven bits long. This optimised bitmap 160may be used to indicate resource multiplexing pattern within theflexible resources 157 as depicted by indicators 158 to 159.

However, in LTE TDD systems, subframes 0, 1, 5 and 6 carry importantchannels/signals such as PSS, SSS and paging channels. If thesesubframes are allocated for D2D communication, the D2D-UEs involved inthat communication may fail to receive system information and messageson these subframes. Therefore, according to yet a further embodiment ofthe present invention, those subframes are fixed for cellularcommunication. As such, the size of the bitmap for TDD systems can befurther reduced by two bits as illustrated in a second method 152.2 foroptimising a bitmap for an LTE TDD communication system.

The second method 152.2 is illustrated with reference to a secondresource multiplexing mask 165 of 10 time units/subframes, wherein thefirst three subframes 166.a are fixed for cellular communication, thefollowing two subframes 167.a are flexibly allocated for cellular/D2D,the followed two subframes 166.b are fixed for cellular communication,and last three time units/subframes 167.b are flexibly allocated forcellular/D2D communication. As such, a further optimised bitmap 170 offive bits long can be provided. The further optimised bitmap 170 may beused to indicate resource multiplexing pattern within the flexibleresources (167.a and 167.b) as depicted by indicators 168 to 169.

FIG. 4 illustrates resource multiplexing masks and corresponding bitmapsfor multiplexing D2D and cellular resources in FDD systems, according toan embodiment of the present invention.

A first method 152.3 for optimising a bitmap for an LTE FDDcommunication system is illustrated, wherein a first resourcemultiplexing mask 175 of 10 time units/subframes is provided. Theresource multiplexing mask 175 includes one time unit/subframe 176.athat is permanently fixed for cellular communication, followed by foursubframes 177.a that are flexibly allocated for either cellular or D2Dcommunication, followed by another one subframe 176.b that is fixed forcellular communication, and last four subframes 177.b are again flexiblyallocated for either cellular or D2D communication.

In LTE FDD systems, DL subframes 0 and 5 may carry important signalssuch as PSS and SSS. On the one hand, if these subframes in DL spectrumare allocated for D2D communication, the D2D-UEs involved in thatcommunication may fail to maintain synchronisation with the system. Onthe other hand, if these subframes in UL spectrum are allocated for D2Dcommunication, there may be severe in-device interference at a receivingD2D UEs that simultaneously receives cellular DL and D2D signals. Insuch case, the important system information would be interfered by D2Dreception.

According to an embodiment of the present invention, these subframes arethus fixed for cellular communication. As a result, an optimised bitmap180 of eight bits long is provided. This optimised bitmap 180 may beused to indicate resource allocation within the flexible timeunits/subframes 177.a and 177.b, as depicted by indicators 178 to 179 inFIG. 4.

In an LTE FDD system, apart from DL subframes 0 and 5 being used forPSS, SSS and paging, DL subframes 4 and 9 are also used for pagingchannel transmission. On the one hand, if these subframes in DL spectrumare allocated for D2D communication, the D2D-UEs involve in thatcommunication may fail to receive paging information. On the other hand,if these subframes in UL spectrum are allocated for D2D communication,there may be severe in-device interference at receiving D2D UEs whosimultaneously receive cellular DL and D2D signals in UL spectrum, inwhich case the important system information would be interfered by D2Dreception. Therefore, it is desirable to fix these subframes forcellular communication. Therefore, the method discussed above can befurther reduced by two bits, as illustrated by method 152.4 of FIG. 4.

The method 152.4 is illustrated with reference to a resourcemultiplexing mask 185 of 10 subframes, wherein the first subframe 186.ais fixed for cellular communication, the following three subframes 187.aare flexibly allocated to cellular or D2D communication, followed by twosubframes 186.b that are fixed for cellular communication, followed byanother three subframes 187.b that are flexibly allocated to D2D orcellular communication, and last subframe 186.c that is also fixed forcellular communication. This results in a further optimised bitmap 190of six bits long. This further optimised bitmap 190 may be used toindicate resource allocation within the flexible time units/subframes187.a and 187.b, as depicted by indicators 188 to 189 in FIG. 4.

FIG. 5 illustrates a plurality of resource multiplexing configurations152.a in TDD systems, according to an embodiment of the presentinvention. The resource multiplexing configurations 152.a may besignalled to the D2D-UEs using either a first bitmap 160 or a secondbitmap 170 in LTE TDD systems.

In one embodiment, the bitmaps 160.a and 170.a may be used in LTE TDDsystems that employ UL/DL configuration 0 or UL/DL configuration 1 orUL/DL configuration 2, to signal a first cellular and D2D multiplexingpattern 152.x, as illustrated in FIG. 5.

In another embodiment, the bitmap 160.b and bitmap 170.b may be used inLTE TDD systems that employ UL/DL configuration 3 or UL/DL configuration4, to signal a second signal cellular and D2D multiplexing pattern152.y, as illustrated in FIG. 5.

In yet another embodiment, the bitmap 160.c and bitmap 170.c may be usedin LTE TDD systems that employ UL/DL configuration 3, UL/DLconfiguration 4 and UL/DL configuration 5, to signal cellular and D2Dmultiplexing pattern 152.z, as illustrated in FIG. 5.

FIG. 6 illustrates a method 300 of resource allocation or multiplexingfor D2D and cellular communication, according to an embodiment of thepresent invention. The method 300 can, for example, be implemented at abase station similar to base station 101.

At block 301, traffic load within the cell coverage is observed,together with interference level reports and requests from D2D-UEs thatare paired or grouped for direct communication with each other. Anappropriate D2D communication interval, a D2D configuration interval andD2D configuration offset are then determined according to the trafficload, the interference level, and the reports and requests. The D2Dcommunication interval can be similar to the D2D communication intervalT₁/151 of FIG. 1, the D2D configuration interval can be similar to theD2D configuration interval T₂/152 of FIG. 1, and the D2D configurationoffset can be similar to the D2D configuration offset T₀/153 of FIG. 1.

At block 302, a resource multiplexing mask is selected, which may, forexample, be one of the masks 155, 165, 175, or 185 described above, toallocate resources for D2D and cellular communications. The resourcemultiplexing mask includes fixed cellular communication subframes, whichcannot be used for D2D communications, and flexible cellularcommunications subframes, which can be used for either cellular or D2Dcommunications.

Subframes are then selected for D2D communication out of the flexiblesubframes within the selected resource multiplexing mask. This selectionmay depend on the spectrum allowed for D2D communication, the UL/DLconfiguration of the cell in TDD systems, cellular traffic conditionswithin the cell, buffer status of the D2D-UEs for D2D communication,and/or a priority of D2D communication over cellular communication.

A bitmap of X bits is then used to indicate which resources areallocated for cellular communication, and which resources are allocatedfor D2D communication, within the selected resource multiplexing mask. Xmay be, for example 10, 8, 7, 6, or 5 bits. For example, cellularresources may be denoted by bit ‘1’ and D2D resources may be denoted bybit ‘0’, or vice versa.

The method 300 further includes configuring an activation time fromwhich the D2D communication interval starts, at block 303.

If the base station is an FDD system (indicated by arrow 306), themethod 300 will further configure restrictions enforced at the basestation with respect to the said D2D-UEs, at block 307. The restrictionsare regarding PDSCH transmission and UL grant transmission, and mayinclude:

-   -   Avoiding PDSCH transmission to D2D-UEs in subframe n if subframe        n+4 has been allocated for D2D communication at the D2D-UEs, and    -   Avoiding UL grant transmission on PDCCH/ePDCCH to D2D-UEs in        subframe n if subframe n+4 has been allocated for D2D        communication at the said D2D-UEs.

If, on the other hand, the base station is a TDD system (indicated byarrow 304), the method 300 will further configure, at block 305,reference UL/DL configuration for PDSCH HARQ-ACK, UL grant and/or PHICHtiming with respect to the D2D-UEs. This is performed to ensure thatsubframe(s) allocated for D2D communication will not impact on thecellular communication.

FIG. 7A and FIG. 7B illustrate a method 350.1 for resource allocation ormultiplexing for D2D and cellular at a UE in an FDD system, according toan embodiment of the present invention.

At block 351.1, D2D resource allocation information is received, forexample from a base station such as the base station 101 of FIG. 1, andpreferably via RRC messaging. The D2D resource allocation informationcan include a D2D communication interval, D2D configuration interval, aD2D configuration offset, resource multiplexing mask information, anactivation time for resource multiplexing and a resource multiplexingbitmap.

If the activation time is not provided, then the D2D-UE will apply theconfiguration from the next coming radio frame. Based upon receivedinformation, a D2D-UE configures a D2D and cellular resourcemultiplexing pattern by applying the resource multiplexing bitmap forthe configured resource multiplexing mask, at block 352.1. As discussedabove, the multiplexing pattern may include fixed resources for cellularcommunication and flexible resources for D2D/cellular communication.

At block 353.1, a D2D scheduling pattern is configured which indicatesthe order of transmission for the D2D-UEs, as discussed above.

A person of ordinary skill in the art will readily appreciate that theprocedures presented in blocks 352.1 and 353.1 may be executed by theD2D-UEs in the same order or in a different order.

Upon configuring the resource allocation patterns for D2D and cellular,the D2D-UEs apply the D2D resource multiplexing pattern after the D2Dconfiguration offset from the configured activation time for D2Dcommunication interval, at block 354.1. The same pattern is repeatedwith the D2D communication interval. After starting D2D and cellularresource multiplexing, the D2D-UEs may perform following operations ateach subframe within the D2D communication interval T₁.

If the current subframe is a D2D subframe in UL spectrum (indicated byarrow 355.1), and it is a transmission opportunity according to the D2Dscheduling pattern (indicated by arrow 356.1), the D2D-UE may receivecellular DL in DL spectrum, and perform D2D transmission in UL, asillustrated by block 370.1.a.

If the current subframe is a D2D subframe in UL spectrum (indicated byarrow 355.1), but it is not a D2D transmission opportunity according tothe D2D scheduling pattern (indicated by arrow 357.1), the D2D-UE mayreceive cellular DL in DL spectrum and/or receive other D2D-UEs' signalsin UL spectrum, as illustrated by block 358.1.a.

If the current subframe is a D2D subframe in DL spectrum (indicated byarrow 359.1), and it is a transmission opportunity according to the D2Dscheduling pattern (indicated by arrow 360.1), the D2D-UE may transmitcellular UL in UL spectrum, and/or may perform D2D transmission in DLspectrum, as illustrated by block 370.1.b.

If the current subframe is a D2D subframe in DL spectrum (indicated byarrow 359.1), but it is not a D2D transmission opportunity according tothe D2D scheduling pattern (indicated by arrow 361.1), the D2D-UEs maytransmit cellular UL in UL spectrum and receive other D2D-UEs' signal inDL spectrum, as illustrated by block 358.1.b.

If current subframe is allocated for cellular transmission (indicated byarrow 362.1), the D2D-UE may perform cellular DL reception and cellularUL transmission, as illustrated by block 363.1.

FIG. 8A and FIG. 8B illustrate a method 350.2 for resource allocation ormultiplexing for D2D and cellular at a UE in a TDD system, according toan embodiment of the present invention.

At block 351.2, D2D resource allocation information is received from thebase station 101, preferably via RRC messages. The D2D resourceallocation information can include a D2D communication interval, a D2Dconfiguration interval, a D2D configuration offset, resourcemultiplexing mask information, an activation time for resourcemultiplexing, a resource multiplexing bitmap, and reference UL/DL timingconfigurations for PDSCH HARQ-ACK, UL grant and/or PHICH. If theactivation time is not configured, the D2D-UE will apply theconfiguration from the next coming radio frame.

Based upon received information, a D2D-UE can configure a D2D andcellular resource multiplexing pattern by applying the resourcemultiplexing bitmap for the configured resource multiplexing mask, atblock 352.2. The D2D and cellular resource multiplexing pattern caninclude fixed resources for cellular communication and flexibleresources for D2D or cellular communication.

At block 352.2_bis, reference UL/DL configuration(s) for PDSCH HARQ-ACK,UL grant and/or PHICH may be configured for cellular communicationduring the D2D communication interval T₁.

Next, at block 353.2 a D2D scheduling pattern may be configured, whichindicates the order of transmission for D2D-UEs. It should be understoodthat the procedures presented in blocks 352.2, 352.2_bis and 353.2 maybe executed by the D2D-UEs in the same order or in a different order.

Upon configuring the resource allocation patterns for D2D and cellularcommunications, the D2D-UEs, at block 354.2, may start applying the D2Dresource multiplexing pattern after the D2D configuration offset fromthe configured activation time for the D2D communication interval, andrepeating the same pattern with the D2D communication interval. Afterstarting D2D and cellular resource multiplexing, the D2D-UEs may performfollowing operations at each subframe within the D2D communicationinterval:

If the current subframe is a D2D subframe (indicated by arrow 355.2),and it is a transmission opportunity according to the D2D schedulingpattern (indicated by arrow 356.2), the D2D-UE may perform D2Dtransmission, as indicated by block 370.2.

If the current subframe is a D2D subframe (indicated by arrow 355.2),but it is not a D2D transmission opportunity (indicated by arrow 357.2),the D2D-UEs may receive other D2D-UEs' signals, as indicated by block358.2.

If the current subframe is allocated for cellular communication(indicated by arrow 362.2), the D2D-UE may perform cellularcommunication, as indicated by block 363.2.

FIG. 9 illustrates a schematic 400 of an exemplary cellularcommunication scenario, according to an embodiment of the presentinvention. The schematic 400 illustrates procedures for cellularcommunication at a base station, such as base station 101, D2D-UEs, suchas D2D-UEs 102, 103, 104, and a legacy UE, such as UE 105, in an FDDsystem when cellular UL resources are shared by D2D-UEs for D2Dcommunication.

The scenario is described with reference to a D2D group comprising afirst D2D-UE A 102, a second D2D-UE B 103 and a third D2D-UE C 104, abase station 101, and a legacy UE 105. The D2D group has been allocatedthree UL subframes per FDD radio frame for D2D communication usingeither a first resource multiplexing mask with bitmap ‘00011111’ or asecond resource multiplexing mask with bitmap ‘000111’.

The scenario 400 may start at SF #0 of radio frame n, at which the basestation 101 transmits a UL grant indicator 401 to D2D-UE A 102 in theDL. The D2D-UE A (102) then transmits UL data 402, corresponding to theUL grant 401, at UL SF #4 of the same radio frame. The UL data 402 isacknowledged by the base station 101 with a NAK in PHICH 403 at DL SF #8of the same radio frame.

According to the current LTE FDD HARQ-ACK timing in UL, the D2D-UE A 102should re-transmit its previous data in UL SF #2 404.a of radio frame(n+1). However, this UL SF #2 has been allocated for D2D communicationfor D2D-UE A 102, therefore, D2D-UE A 102 may wait until the nextavailable UL cellular subframe at SF #4 of radio frame (n+1) to performa re-transmission 404.

Corresponding to the re-transmission 404, the base station 101 maytransmit an ACK in PHICH 405 at DL SF #8 of radio frame (n+1). The basestation 101 then transmits a UL grant 406 to D2D-UE C 104 in DL SF #1 ofradio frame n, which aligns with the first D2D opportunity of D2D-UE C104 in the UL spectrum. Corresponding to the UL grant 406, the D2D-UE C104 may perform the UL data transmission 407 at UL SF #5 of the sameradio frame, and the base station 101 may send a NAK in PHICH 408 of DLSF #9 of the same radio frame.

Corresponding to the NAK 408, the D2D-UE C 104 should perform there-transmission at UL SF #3 409.a of radio frame (n+1). However, this ULSF #3 has been allocated for D2D communication for the same D2D-UE C104, therefore, the re-transmission 409 may be delayed until the nextavailable UL cellular SF, which occurs at SF #4 of radio frame (n+1),and the base station (101) may send an ACK in PHICH (410) at DL SF #8 ofradio frame (n+1).

A DL data transmission 411 to the D2D-UE B 103 from base station 101 issent at DL SF #2 of radio frame n, which aligns with the UL SF #2 of thesame radio frame allocated for D2D transmission for the D2D-UE B 103.D2D-UE B 103 acknowledges this DL data 411 at UL SF #6 of the same radioframe with an ACK 412.

Next, in DL SF #7 of radio frame n, the base station may transmit DLdata 413 to the legacy UE 105, which then may send a NAK 414 to the basestation at UL SF #2 of radio frame (n+1) that has been used for D2Dtransmission within the D2D group 102.a. Corresponding to the NAK 414,the base station 101 may schedule a re-transmission 415 at DL SF #8 ofthe radio frame (n+1). The legacy UE may send an ACK 416 for the saidre-transmission 415 in the UL SF #2 of radio frame (n+1), which has alsobeen used for D2D communication within the D2D group.

Finally, another UL grant 417 for D2D-UE B (103) is sent at DL SF #7 ofradio frame (n+1). Corresponding to the said UL grant 417, the D2D-UE B103 should send the UL data at UL SF #1 (418.a) of radio frame (n+2).Since this UL SF #1 has been allocated for D2D communication for thesame D2D-UE 103, the UL data transmission may be delayed until the nextcellular UL SF #4 of the radio frame (n+2).

FIG. 10 illustrates a schematic 450 illustrating the procedures forcellular communication at a base station, D2D-UEs, and a legacy UE in aTDD system when cellular resources are shared by D2D-UEs for D2Dcommunication, according to an embodiment of the present invention.

The base station can be similar or identical to the base station 101 ofFIG. 1, the D2D-UEs can be similar to the UEs 102, 103, 104, 106, and107 of FIG. 1, and the legacy UE can be similar to the legacy UE 105 ofFIG. 1.

The base station, which uses TDD UL/DL configuration 0, communicateswith a D2D group 102.a comprised of D2D-UE A (also denoted as 102),D2D-UE B (also denoted as 103) and D2D-UE C (also denoted as 104), aone-to-one communication pair (106.a) comprised of D2D-UE D (alsodenoted as 106) and D2D-UE E (also denoted as 107), and a legacy UE(also denoted as 105). The D2D group 102.a has been allocated four ULsubframes per TDD radio frame for D2D communication using a resourcemultiplexing mask with either a bitmap of ‘0011100’ or with bitmap‘00100’. The D2D pair (106 and 107) have been allocated two UL subframesper TDD radio frame for one-to-one communication 106.a using a resourcemultiplexing mask either with bitmap of ‘1011110’ or bitmap ‘10110’.

The base station 101 may configure the D2D group 102.a with referencetiming configuration for PDSCH HARQ-ACK transmission in UL as UL/DLconfiguration 2 while timing configuration for UL grant and PHICHtransmission in DL may remain same as UL/DL configuration 0. The basestation may also configure D2D pair (106 and 107) involved in one-to-onecommunication with reference timing configuration for PDSCH HARQ-ACKtransmission in UL as UL/DL configuration 1 while timing configurationfor UL grant and PHICH transmission in DL may remain same as UL/DLconfiguration 0.

The cellular communication scenario in 450 may start at SF #0 of the nthradio frame at which the base station 101 may transmit a UL grant withMSB=1 and LSB=0 (as depicted in 451) to the legacy UE 105 while it mayalso transmit DL data (depicted by 456) to the D2D-UE-A 102 in D2D group102.a. Corresponding to the UL grant 451 transmitted to the legacy UE105, the legacy UE 105 may transmit UL data 452 on SF #4 of radio framen, which has been allocated for D2D communication in D2D group 102.a andD2D pair (106 and 107), to the base station 101. The base station maythen send a NAK in PHICH with I_(PHICH)=1 (depicted by 453) to thelegacy UE 105 at SF #0 of radio frame (n+1) according to the UL grantand PHICH timing of UL/DL configuration 0.

Upon reception of NAK (453) the legacy UE 105 may re-transmit its ULdata (depicted by 454) at SF #7 of radio frame (n+1) to the base station101, which then may send ACK in PHICH with I_(PHICH)=0 (depicted by 455)to the legacy UE 105 according to the PHICH timing of UL/DLconfiguration 0. With respect to the DL data (depicted by 456)transmitted to the D2D-UE A 102 on DL SF #0 of radio frame n, D2D-UE A102 may send ACK/NAK on SF #7 of the same radio frame to the basestation 101 according to the UL/DL configuration 2 which is thereference timing configuration for PDSCH HARQ-ACK transmission in D2Dgroup 102.a.

The base station 101 may then transmit DL data (depicted by 458) toD2D-UE E 107 of the one-to-one communication pair 106.a and a UL grantwith MSB=1 and LSB=0 (depicted by 460) to D2D-UE C 104 of the D2D group102.a simultaneously in the DL part of the SF #1 of radio frame n. Withrespect to the DL data (depicted by 458) the D2D-UE E 107 may transmitan ACK/NAK message 459 to the base station 101 at SF #7 of the sameradio frame according to the UL/DL configuration 1 which is thereference timing configuration for PDSCH HARQ-ACK transmission in theone-to-one communication group 106.a. Meanwhile, in response to the ULgrant (depicted by 460), D2D-UE C 104 may transmit its UL data 461 in SF#7 of the same radio frame, according to the UL grant timing of UL/DLconfiguration 0, to the base station 101 which then may send a NAK inPHICH with I_(PHICH)=0 (depicted by 462) to the D2D-UE C 104 in the DLpart of the SF #1 of radio frame (n+1). Upon reception of the NAK 462,the D2D-UE C 104 may re-transmit UL data (depicted by 463) in SF #7 ofthe radio frame (n+1) to the base station 101, which may then send amACK in PHICH with I_(PHICH)=0 (depicted by 464) to D2D-UE C 104 in theDL part of the SF #1 of radio frame (n+2) according to the PHICH andre-transmission timing rules of UL/DL configuration 0.

At the DL SF #5 of radio frame n, the base station 101 may send DL data(depicted by 465) to D2D-UE B 103 of D2D group 102.a and DL data(depicted by 467) to the legacy UE 105 simultaneously. These DLtransmission may be acknowledged by D2D-UE B 103 in SF #2 of radio frame(n+1) at 466 according to reference PDSCH HARQ-ACK timing of UL/DLconfiguration 2, and by the legacy UE 105 in SF #9 of radio frame n 468,which has been allocated for D2D communication in D2D group 102.a andone-to-one communication pair 106.a, according to PDSCH HARQ-ACK timingof UL/DL configuration 0.

In the exemplary scenario 450, the base station 101 may transmit a ULgrant with MSB=1 and LSB=1 (depicted by 469) to the D2D-UE D 106 in theDL part of the SF #6 of radio frame n. This UL grant may trigger ULtransmissions by D2D-UE D 106 at SF #2 (depicted by 470) and SF #3(depicted by 471) of radio frame (n+1) according to UL grant timing ofUL/DL configuration 0. The base station 101 may send an ACK on PHICHwith I_(PHICH)=0 (depicted by 472) corresponding to the UL data 470 inSF #6 of radio frame (n+1) while it may send a NAK on PHICH withI_(PHICH)=0 (depicted by 473) on DL SF #0 of radio frame (n+2) accordingto the PHICH timing of UL/DL configuration 0. In response to the NAKreceived in SF #0 of radio frame (n+2) D2D-UE D 106 should re-transmitits UL data (depicted by 471) in SF #4 of radio frame (n+1) according toPHICH assignment and re-transmission timing of UL/DL configuration 0.However, this UL SF #4 has been allocated for D2D communication atD2D-UE D 106, which results in a D2D and PUSCH collision. In order toresolve this issue, the base station 101 may also send a UL grant withMSB=0 and LSB=1 (depicted by 473) at SF #0 of radio frame (n+2) tore-configure the UL re-transmission to SF #7 of radio frame (n+2). Basedupon the UL grant in 473, D2D-UE D 106 may perform the re-transmission(depicted by 474) at SF #7 of radio frame (n+2).

In SF #0 of radio frame (n+2), the base station 101 may also schedule DLdata for D2D-UE B 103 at 475 and the legacy UE 105 at 477. Thesetransmissions will be acknowledged by D2D-UE B 103 in SF #7 (depicted by476) of the same radio frame according the PDSCH HARQ-ACK referencetiming of UL/DL configuration 2, and by the legacy UE 105 in SF #4(depicted by 477), which has been allocated for D2D communication in D2Dgroup 102.a and one-to-one pair 106.a, according to the PDSCH HARQ-ACKtiming of UL/DL configuration 0.

FIG. 11 illustrates a method 370 of performing D2D communication withina group of D2D UEs in resources allocated for D2D communication,according to an embodiment of the present invention.

The method 370 may be applied to D2D-UEs in a D2D group (such as 102.a)that has already received D2D resource allocation information from thebase station 101 preferably in the form of resource allocation maskinformation as described earlier. Within the said D2D group, there maybe a group owner/master who decides the scheduling pattern for theD2D-UEs within the group depending on the buffer status and thepriorities of each member of the group and transmits the pattern to thegroup. The scheduling pattern may be a sequence that shows who shouldtransmit next in the D2D resources. The scheduling pattern may berepeatedly applied by the D2D-UEs in the group to determine which UEshould transmit in each D2D resource.

According to certain embodiments, A D2D-UE in the group may send ACK/NAKfeedback for other transmissions piggybacked with its own datatransmission during the transmission opportunity assigned for the saidD2D-UE.

The method 370 is based on a set of rules as described below.

According to certain embodiments, a D2D-UE in the D2D group transmitsone or multiple ACK/NAK feedback messages, addressed to one or moreother D2D-UEs in the group, piggybacked with its own data transmissionin their respective transmission opportunities. The one or multiplefeedback messages may contain an ACK/NAK for most recently received‘non-expired data’ from each D2D-UE in the said D2D group. Here,‘non-expired data’ refers to data received from another D2D-UE in thegroup for which the other D2D-UE has not yet received a re-transmissionor new transmission opportunity.

A D2D-UE that performs a D2D transmission on subframe n may expectfeedback for its transmission on or after subframe n+k. Preferably k=4.

Upon receiving feedback from another D2D-UE in the group on subframe n,a D2D-UE may apply the received feedback on its next scheduledtransmission on or after subframe n+1 where l>=1.

According to certain embodiments of the present invention, a D2D-UE mayperform re-transmission if all received feedback until its nexttransmission opportunity are NAKs or if no feedback is received untilits next transmission opportunity. In other words, a D2D-UE in the D2Dgroup may not re-transmit if at least one positive acknowledgement isreceived before its next scheduled transmission opportunity.

The method 370 may be used by a D2D-UE (e.g. 102 or 103 or 104) that isgiven an opportunity to transmit in the D2D group. In such case, thefollowing operations are be performed by a D2D-UE (102, 103, 104) on thegiven transmission opportunity.

If the current transmission opportunity is the first transmissionopportunity (as depicted by arrow 371.a), and if there is no ACK/NAKfeedback ready for others transmission received k subframes before (asdepicted by arrow 372.a), where k>=4, the D2D-UE (102 or 103 or 104) maytransmit new data only (as depicted by block 373).

If the current transmission opportunity is the first transmissionopportunity (as depicted by arrow 371.a), and there is ACK/NAK feedbackready for others transmission received k subframes before (as depictedby arrow 372.b), where k>=4, the D2D-UE (102 or 103 or 104) may transmitnew data and ACK/NAK feedback together (as depicted by block 374). Asdescribed earlier, this ACK/NAK feedback transmission may be piggybackedwith data transmission.

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes haveelapsed after its previous transmission (as depicted by arrow 375.a),and if at least one ACK received l subframes before (as depicted byarrow 376.a) for its most recent transmission, where l>=1, and if thereis no ACK/NAK feedback corresponding to others' transmission received ksubframes before (as depicted by arrow 372.a) ready, where k>=4, theD2D-UE (102 or 103 or 104) may transmit new data only (as depicted byblock 373).

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes haveelapsed after its previous transmission (as depicted by arrow 375.a),and if at least one ACK received l subframes before for its most recenttransmission (as depicted by arrow 376.a), where l>=1, and if there isACK/NAK feedback corresponding to others' transmission received ksubframes before, ready (as depicted by arrow 372.b), where k>=4, theD2D-UE (102 or 103 or 104) may transmit its new data and ACK/NAKfeedback together (as depicted by block 374). As described above, thisACK/NAK feedback transmission may be piggybacked with data transmission.

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes haveelapsed after its previous transmission (as depicted by arrow 375.a),and if there is no ACK received for its most recent transmission, 1subframes before (376.b), where l>=1, and if there is ACK/NAK feedbackcorresponding to others transmission received k subframes before, ready(as depicted by arrow 377.a), where k>=4, the D2D-UE (102 or 103 or 104)may re-transmit its most recently transmitted data together with ACK/NAKfeedback (as depicted by block 379). As described above, this ACK/NAKfeedback transmission may be piggybacked with data transmission.

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes haveelapsed after its previous transmission (as depicted by arrow 375.a),and if there is no ACK received for its most recent transmission, 1subframes before (376.b), where l>=1, and if there is no ACK/NAKfeedback ready for others transmission received k subframes before (asdepicted by arrow 377.b), where k>=4, the D2D-UE (102 or 103 or 104) mayre-transmit most recently transmitted data only (as depicted by block378).

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes have notelapsed after its previous transmission (as depicted by arrow 375.b),and if there is no ACK/NAK feedback corresponding to others transmissionreceived k subframes before, ready (as depicted by arrow 372.a), wherek>=4, the D2D-UE (102 or 103 or 104) may transmit its new data only (asdepicted by block 373).

If the current transmission opportunity is not the first transmissionopportunity (as depicted by arrow 371.b), and if k subframes have notelapsed after its previous transmission (as depicted by arrow 375.b),and if there is ACK/NAK feedback corresponding to others transmissionreceived k subframes before, ready (as depicted by arrow 372.b), wherek>=4, the D2D-UE (102 or 103 or 104) may transmit its new data andACK/NAK feedback together (as depicted by block 374). As describedabove, this ACK/NAK feedback transmission may be piggybacked with datatransmission.

FIG. 12 illustrates a schematic 100.b of an exemplary D2D communicationscenario in a D2D group such as 102.a, and a schematic 500 illustratinga corresponding timing diagram, according to an embodiment of thepresent invention.

In the exemplary scenario 100.b, three D2D UEs, namely UE-A 102, UE-B103 and UE-C 104 communicate with each other according to the schedulingpattern ‘BAC’ which indicates that D2D-UE B 103 will transmit firstfollowed by D2D-UE A 102 and then D2D-UE C 104. Furthermore, the D2D-UEshave been allocated four subframes per radio frame for D2Dcommunication, preferably using one of the earlier described resourcemultiplexing masks described in accordance with one novel aspect of thepresent invention.

Accordingly, at the first D2D communication opportunity (as depicted by501), the D2D-UE B 103 will transmit data B1 (depicted by 502) for thefirst time to D2D-UE A 102 and D2D-UE C 104. Next, at the second D2Dcommunication opportunity (depicted by 503), which occurs immediatelyafter the first communication opportunity 501, the D2D-UE A 102 willtransmit data A1 (depicted by 504) for the first time. At the occurrenceof this opportunity (503), D2D-UE A 102 may not have completedprocessing the data received from D2D-UE B 103, therefore, the ACK/NAKfor that data (502) is not ready for transmission by D2D-UE A 102.

As illustrated, a third D2D opportunity (depicted by 505) occurs threesubframes after the second opportunity (503). At this third opportunity(505), D2D-UE C 104 transmits its data C1 together with any feedbackready for other UEs. Since the third D2D opportunity (505) occurs fouror more subframes after previous two transmissions, ACK/NAK feedback forthose transmissions (502 and 504) may be ready at D2D-UE C 104. Thus,D2D-UE C 104 transmits its data C1 along with NAK for A1 and ACK for B1at 506. At a fourth D2D opportunity (depicted by 507), which occursimmediately after the third opportunity (505), D2D-UE B 103 again getsthe opportunity to transmit. By this time it has feedback ready for dataA1 (504), but not for data C1 (506). Further, assuming that a D2D-UE canapply feedback one subframe after receiving the feedback (i.e. l=1),D2D-UE B 103 has received one ACK from D2D-UE C 104 at 506 for itsprevious transmission B1 (502). Therefore, D2D-UE B 103 will transmitnew data B2 along with NAK for A1 at 508.

A fifth D2D opportunity (509) occurs at the fourth subframe after thefourth opportunity (507), and the D2D-UE A 102 gets a turn to transmit.At this stage, D2D-UE A has received two feedbacks from D2D-UE B 103 andD2D-UE C 104 for its previous transmission A1 (504), and both of themare NAK. Therefore, D2D-UE A 102 re-transmits its previous data A1 atthe fifth D2D opportunity (509). Further, D2D-UE A 102 has feedbackready for data B1, B2 and C1 received after its previous transmission.However, D2D-UE B 103 has already completed the transmission cycle fordata B1 because it has already transmitted data B2 based on the feedbackfor data B1. Therefore, at the fifth D2D opportunity (509), data B1 has‘expired’. Thus, D2D-UE A 102 may not transmit feedback for data B1, butfor data B2 and C1. As a result, D2D-UE A 102 may transmit data A1 alongwith NAK for data B2 and ACK for data C1 (depicted by 510).

Next, at a sixth D2D opportunity (depicted by 511), D2D-UE C 104 gets asecond turn to transmit. At this point, D2D-UE C 104 has received oneACK from D2D-UE A 102 for its previous data C1. Therefore, D2D-UE C maytransmit new data C2. Further, D2D-UE C 104 has feedback ready for dataB2 among the transmissions received after its previous transmissionopportunity (505). Thus, D2D-UE C 104 may transmit data C2 along withACK for B2 (depicted by 512). A seventh D2D opportunity (depicted by513) occurs at the fourth subframe after the sixth opportunity (511),and D2D-UE B 103 gets its third opportunity to transmit. According tothe previously described rules, D2D-UE B 103 transmits new data B3 alongwith ACK for A1 and ACK for C2 (depicted by 514). The final D2Dopportunity (depicted by 515) occurs at the last subframe of the frame(n+1), at which point D2D-UE A 102 transmits new data A2 and ACK for C2(516).

In the present specification and claims (if any), the word ‘comprising’and its derivatives including ‘comprises’ and ‘comprise’ include each ofthe stated integers but does not exclude the inclusion of one or morefurther integers.

Reference throughout this specification to ‘one embodiment’ or ‘anembodiment’ means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more combinations.

In compliance with the statute, the invention has been described inlanguage more or less specific to structural or methodical features. Itis to be understood that the invention is not limited to specificfeatures shown or described since the means herein described comprisespreferred forms of putting the invention into effect. The invention is,therefore, claimed in any of its forms or modifications within theproper scope of the appended claims (if any) appropriately interpretedby those skilled in the art.

This application is based upon and claims the benefit of priority fromAustralian provisional patent application No. 2014901540, filed on Apr.29, 2014, the disclosure of which is incorporated herein in its entiretyby reference.

REFERENCE SIGNS LIST

-   100 wireless communication system-   101 access node-   101.a first coverage-   102-107 user equipment (UE)-   102.a D2D group-   106.a D2D-pair

1. A wireless communications method implemented in a user equipment usedin a wireless communications system, the method comprising: receiving,from a base station, first information and second information, the firstinformation indicating a communication interval, and the secondinformation indicating a resource allocation, wherein the resourceallocation starts after the configuration offset which is relative tosubframe 0; and communicating other user equipment on resourcesdetermined based on the first information and the second information. 2.A wireless communications method implemented in a base station used in awireless communications system, the method comprising: transmitting, toa user equipment, first information, and second information, the firstinformation indicating a communication interval, and the secondinformation indicating a resource allocation, wherein the resourceallocation starts after the configuration offset which is relative tosubframe 0; and communicating the user equipment on resources determinedbased on the first information and the second information.